Process for the preparation of diphenylamines



PROCESS FOR THE PREPARATION OF DIPHENYLAMINES Robert K. Miller, NewCastle, Del., assignor to E. I. du Pont de Nemonrs and Company,Wilmington, Del., a corporation of Delaware N Drawing. Application March30, 1959 Serial No. 802,664

Claims. (Cl. 260-576) The present invention is directed to a novelmethod for producing diphenylamines; this invention is particularlyuseful in the preparation of unsymmetrical diphenylamines.

This application is a continuation-in-part of copending applicationsSerial No. 592,732, filed June 21, 1956 and application Serial No.598,736, filed July 19, 1956, both applications now abandoned.

Diarylamines have long been important intermediates in the chemicalindustry. Recently they have been employed in the preparation ofphenothiazines, particularly ring-substituted phenothiazines which arefurther converted into such -N-substituted phenothiazines as -(3dimethylaminopropyl)-2chlorophenothiazine, a tranquilizing agent inmedicinal use known as chloropromazine (see US. Patent 2,645,640 andBritish Patent 716,205).

Several general routes to diarylamines are known. One typical method,suitable for the preparation of symmetrical diphenylamines, consists ofheating the primary aromatic amine with its corresponding hydrochloride,e.g., aniline and aniline hydrochloride yield ammonium chloride anddiphenylamine; it is impractical for preparing unsymmetricaldiphenylamines; e.g., heating aniline hydrochloride with toluidine givesa difiicultly separable mixture of diphenylamine, methyldiphenylamineand dimethyldiphenylamine. More practical for the preparation ofunsymmetrical diphenylamines is the Ulhnann condensation which may beused in several modifications, all

involving reaction of an aryl halide with an aryl amine in the presenceof an activating substituent and a copper catalyst. In one modification,an ortho-haloaromatic carboxylic acid is condensed with an aromaticprimary amine and the resulting orthocarboxy diarylamine is thenthermally decarboxylated, e.g., 3-chlorodiphenylamine is obtained fromeither (a) 2,4-dichlorobenzoic acid and aniline or (b) 2-chlorobenzoicacid and 3-chloroaniline. A variation on the above method involvesreacting anthranilic acid with bromobenzene to obtain the intermediateN-phenyl-anthranilic acid.

These processes sufler a major disadvantage in that introducing theactivating carboxyl group into the reactant is costly and thediarylamine is obtained at the expense of the carboxyl group which islost as CO in an additional unit operation.

Another known routine to the preparation of diarylamines employs an arylamine which is activated by a nitro group, such as o-nitroaniline or byan N-acetyl group. It is known that acetanilide and bromobenzene yieldN-acetyl-diphenylamine, hydrolyzable to diphenylamine on heating inalcoholic hydrochloric acid for 3 hours (Goldberg, Berichte 40, 4541(1907)); that N- acetyl 0- (or p-) toluidine yields N-acetylmethyldiphenylamine, saponifiable in hot alcoholic alkali to the 0- (orp-) methyldiphenylamine. (Weston and Adkins, Journ. Am. Chem. Soc. 50,859 (1928).)

One disadvantage of this known method utilizing an 'N-acetyl group isthat a time consuming costly hydroyltic step is required to remove theactivating group. In the absence of the activating nuclear carboxylgroup or the N-acetyl group, the reaction is either impractically slug-United Sttes atent 0 p CC gish or fails entirely. It is highly desirablethat the activating group be easily and economically removed after ithas served its purpose. Even with the activating N-acetyl group, thereaction is rather slow, about 20 to 24 hours at elevated temperaturesbeing required to achieve practical yields of the product of thecondensation.

It is an object of the present invention to utilize formanilides in theUllmann condensation with aryl halides wherein the diarylamine isdirectly recoverable from the reaction mass.

it is a further object of this invention to eliminate the need forprolonged hydrolysis of the reaction product obtained from N-acetylprimary aromatic amine and aryl halide.

It is a further object of this invention to produce unexpectedly highyields of diarylamine.

It is a specific object of the present invention to provide a simplifiedand economically practical Ullmann condensation method for preparing3-chlorodiphenylamine.

It is a specific object of the present invention to provide a simplifiedand economically practical Ullmann condensation method for preparingboth symmetrical and unsymmetrical diphenylamines.

The present invention is based on the use of formanilides in lieu of theprior art acetanilides in the production of diphenylamines oncondensation with aryl halides in the presence of a copper Ullmanncondensation catalyst and potassium or sodium carbonate as acidacceptors. It has been discovered that, when formanilides rather thanthe acetanilides suggested in the prior art are employed in the Ullmanncondensation, the reaction time is significantly shortened and theproduct of the condensation obtained in higher yield.

In one embodiment of the present invention symmetrical and unsymmetricaldiphenylamines are obtained by reacting (A) a compound taken from thegroup consisting of formanilide and the alkyl, alkoxyl, fluoro andchloro substituted formanilides with (B) a compound taken from the groupconsisting of bromobenzene, iodobenzene and alkyl, alkoxyl, fluoro andchloro substituted bromo and iodobenzenes in the presence of a copperUllmann condensation catalyst and potassium carbonate at a temperaturewithin the range of -240 C. and recovering the diphenylamine from thereaction mass.

It has also been discovered that when potassium carbonate is employed asthe acid-acceptor in this condensation the diphenylamines rather thanthe expected N-acyl diphenylamines are obtained directly from thereaction mass as the major product. Thus the hydrolytic step of theprior art is no longer necessary and the process is unexpectedlysimplified. Furthermore, use of a formanilide materially shortens therequired time and the overall yield of the diphenylamine issubstantially as good as or better than that obtained following the oldpractice.

Another embodiment of the present invention comprises reacting (A) aformanilide with (B) bromobenzene in the presence of a copper Ullmanncondensation catalyst and sodium carbonate at a temperature within therange of 170 -240 C. and recovering the diphenylamine from the reactionmass after hydrolyzing the reaction product.

The prior art describes the use of a wide variety of acetanilides andphenyl bromides (and iodides) in the Ulhnann condensation reaction; thatis, these reactants may contain alkyl, alkoxyl, chloro and fluorogroups, all of which are inert under the conditions of the condensationreaction as more fully described below. Thus, proper selection of theorganic reactants afiords N-acety ldiphenylamines which are substitutedin one phenyl ring by one or more substituents and are unsubstituted inthe 3 other phenyl ring or which are substituted in both phenyl rings bythe same or different groups which may occupy the same or diiferentpositions on the two phenyl rings.

The point of the invention resides in the presence of the N-forniylgroup and is independent of the presence of other siib'stituents on thephenyl rings in the organic reactants so long as these othersubstituents are inert (i.e., unaltered) under the conditions of theUllmann condensation. Alkyl, alkoxyl and halo groups other than bromoand iodo are inert substituents in this reaction and may be present ineither of the organic reactants. p

The alkyl substituents are preferably lower-alkyl groups of from 1 to 4carbon atoms, particularly methyl and ethyl, for reasons of economy andavailability of the subject intermediates. Likewise the preferredalkoxyl groups are methoxyl, ethoxyl, propoxyl, and butoxyl, particularly methoxyl. A fluoro or chloro group, incontr'ast to bromoor iodo-, isrelatively inert under conditions of the reaction, and, as indicatedabove, may be present in either of the reactants;

Representative formanilides which may be employed according to themethod of this invention are: formanilide, m-fluoroformanilide,m-chloroformanilide, N- formyl-o- (or p-) toluidine,N-formyl-m-ethylaniline, mmethoxyformanilide, 2,4-dimethylformanilide,and the like as defined.

Representative phenylhalides are: bromobenzene, iodobenzene,p-bromotoluene, m-fluoro-bromobenzene, p-iodochlorobenzene,m-methoxybromobenzene, p methoxybromobenzene, 2,4-dimethylbromobenzene,and the like.

In general, any of the formanilides may be employed with any of thephenyl bromides or iodides for the preparation of symmetrical orunsymmetrical diphenylamines. The method of this invention isparticularly useful for preparing unsymmetrical diphenylamines, sincesuch amines are difiicultly or not at all obtainable free of isomers bythe more conventional methods. Thus by proper selection of the organicreactants, diphenylamines may be obtained which are substituted in onephenyl ring by one or more substituents and unsubstituted in the other;or which are substituted in both phenyl rings by the same or diiferentgroups which may occupy the same relative positions or differentpositions on the two phenyl rings.

Representative diphenylamines which may be prepared according to thepresent invention are diphenylamine, 2- and 4-methyldiphenylamine,2,4'-dimethyldiphenylamine (ditolylamine), 3,4,3,4'tetramethyldiphenylamine, 3- fluorodiphenylamine, 3 chlorodiphenylamine,3,3 -dichlorodiphenylamine, 3 -methoxydipheny1amine, 4-methoxydiphenylar'nine, 3 methoxy 3' methyldiphenylamine, and the likeas defined above. In the preferred embodiment of the invention,3-chlorodiphenylamine is prepared by reacting m-chloroformanilide(N-formyl-n1- chloroaniline) with bromobenzene.

Except for the use of a formanilide rather than an acetanilide, thepresent process follows the practice of the art with regard to thegeneral reaction conditions. Best results are generally obtained in theabsence of solvent or diluent, while employing substantially anhydrousmaterials under anhydrous conditions. In the preferred general method, amixture consisting of a formanilide, such as N-forrnyl-m-chloroaniline,an aryl halide such as bromobenzene, and potassium carbonateacid-acceptor and an Ullmann condensation catalyst such as copper or acompound of copper is heated to and held at temperatures ranging fromabout 170 to 220 C. at normal pressures, until stoichiometricequivalents of the organic reactantsare substantially consumed.

a It is preferred to employ approximately stoichiometric quantities ofthe organic reactants in the absence of addi- 'tional solvent ordiluent. If, desired, however, either of the organic reactants may be inexcess. In the preparation of th e preferred S-chlor'odiphenyIamine, forexample, best results are obtained if bromobenzene is employed in notmore than 50 mol percent excess and for reasons of economy not more than5 mol percent excess. When relatively large excesses of bromobenzene arepresent,

the refluxing excess tends to maintain the reaction mass at the lowertemperaturelimit, and, unless superatmospheric' pressures are employedto raise the boiling point of the mixture, the time required to completethe condensation is materially lengthened. An excess of N-formyl-m-chloroaniline of up to about 20 mol percent is practical;however, as stated above, for best results and for reasons of economy,approximately stoichiometric quantities of organic reactants areemployed.

The rate of condensation becomes practical at temperatures ofapproximately :5 C. and above. With bromobenzene as the aryihalide, thisinitial lower temperature corresponds to the reflux temperature of themixture. While external heat is being applied, the reflux temperature ofthe mass rises as bromobenzene is consumed. Although the reactionproceeds at the lower end of the stated temperature range it ispreferred to allow the temperature of the reaction mass to rise toZOO-220 C. Loss of the formyl' group (when potassium carbonate is theacid-acceptor) takes place more rapidly at the higher than at the lowertemperatures. Temperatures of up to about 240 C. may be employed. Ingeneral no further advantages are gained on exceeding 240 C., and it isseldom necessary to exceed 220 C. to achieve an economically practicalrate of reaction. The heat input is then regulated to maintain the massat these temperatures, preferably at about 210 C. In the condensationstep, the formyl derivatives are remarkably more reactive than thecorresponding acetyl derivatives. For example, the time required toreach the maximum preferred temperature is cut by a factor of about 4when m-chloroacetanilide is replaced by m-chloroformanilide undercomparable. conditions; the holding time at the higher temperature tocomplete the condensation is also shortened with the result that theoverall reaction time is cut in half. The actual times required dependupon such factors as the particular organicreactants and their molratios, and on the nature of and quantities of the copper catalyst andacid-acceptor.

A variety of Ullmann condensation catalysts may be employed. By Ullmanncondensation catalyst is meant metallic copper in suitable form andcompounds of copper which are normally engaged in the art to elfectcondensations of this type. Representative and suitable catalysts arecopper powder, copper-bronze powder, copper and iodine mixture, copperhalides such as cuprous iodide, cuprous bromide and cuprous chloride,cupric carbonate, cupric acetate and the like described in the art,preferably cupric carbonate. Only relatively small quantities ofcatalyst are required; practical quantities are from about 1 to 10% byweight of the formanilide. Lesser quantities do not always provide forconsistently practical rates of condensation, while larger quantities,though operable, do not always provide additional advantagescommensurate with increased cost. About 3% by weight of cupric carbonateis preferred.

The acid-acceptor, potassium or sodium carbonate, will be employed inquantities providing from one to three equivalents, preferably at leasttwo equivalents (one molar equivalent), based on the theoreticalquantity of halide to be produced in the metathetical reaction betweenthe formanilide and the aryl halide reactants.

The detailed mechanism of the present invention wherein potassiumcarbonate is the acid-acceptor and wherein the formyl group is removedis not known with certainty; it appears that this unexpected result isintimately associated with potassium bicarbonate which is produced insitu in the reaction mass. A possible explanation is that the potassiumbicarbonate decomposes, in the temperature range employed, intopotassium carbonate, CO and H 0; said water produced in situ removes theforrnyl group from the N-forinyldiphenylamine.

As stated earlier, Ullmann condensations of the present type proceedbest using anhydrous substances under anhydrous conditions. However, inthe present invention it is not critical to prepare and maintaincompletely anhydrous reactants and reagents. To do so is inconvenient,time-consuming and costly. Instead, we employ materials which arenormally considered by those skilled in the art to be anhydrous, i.e.,not obviously grossly contaminated. In practice small quantities ofwater invariably begin to appear in the refluxing vapor in the initialstages of the reaction. At the reaction temperatures employed the wateris readily removed from the reaction zone as the azeotrope with the arylhalide, e.gl, bromobenzene.

The diphenylamine produced according to the method of this invention,with potassium carbonate as acidacceptor, is readily isolated from thecrude reaction mass in high yield under non-hydrolytic conditions. Thereaction mass may be extracted with an organic solvent such as benzene,chlorobenzene, o-dichlorobenzene and the like to separate the organicfrom inorganic components, and the extract evaporated to recover thecrude product, which, if desired, may be distilled, or crystallized fromconventional solvents. Alternately, the reaction mass may be drowned inwater, the organic layer separated and either distilled or crystallizedin the usual way. Steam-volatile products such as diphenylamine may besteam distilled directly from the reaction mass. Occasionally it isfound that the crude products contain up to 10% of carbonyl compounds,calculated as the N- formyldiphenylamine. These may be removed byfractionally distilling the organic product, or where the diphenylamineis a solid, by crystallization from solvents.

m-Chloro-diphenylamine prepared according to the method of thisinvention is suitable for the preparation of 2-chloro-phenothiazinefollowing the procedures described in the art.

Example 1 A mixture consisting of 226.4 parts (1.87 mols) formanilide,294 parts 1.87 mols) bromobenzene, 345.2 parts (2.5 mols) potassiumcarbonate, and 5 parts (0.04 mol) cupric carbonate was heated to reflux(168 C.) while being stirred. During this time, any two-phase condensatewhich appeared was separated in an azeotropic distillation head, thewater being discarded and the bromobenzene returned to the reactionvessel. The temperature of the mass rose from 168 C. to 205 C. in 2.5hours. The external source of heat was then regulated to maintain thecontents of the reaction vessel at 210i5 C. for hours. The charge wascooled to about 100 C., thoroughly extracted with chlorobenzene (600parts) and filtered. The filtrate was stripped of chlorobenzene underreduced pressure and distilled at 10 to mm. Hg pressure: 261.2 parts(82.6% yield) of diphenylamine were collected, boiling in the range 155to 175 C. and melting in the range 36 to 48 C. Analysis of the infraredspectrum showed less than 5% of carbonylcontaining substance, calculatedas N-formyldiphenylamine. Recrystallized from a 1:2 mixture of benzeneand petroleum ether this product melted at 49.5-51.5 C. (no depressionon admixture with authentic diphenylamine, M.P. 53 C.), and had nocarbonyl band in its infrared spectrum which was identical to that ofauthentic diphenylamine.

Equally good or somewhat better yields are obtained on working up thereaction mass by alternate methods: For example, (a) the benzene extractof the reaction mass, instead of being distilled is concentrated tosmall volume, diluted with petroleum ether and chilled to obtain purecrystalline diphenylamine; (b) the reaction mass is drowned in water,the organic components removed and distilled to obtain pure productboiling at 160-165" C. and 5 mm. Hg pressure; (c) the reaction mass isdrowned in water and steam distilled to recover the diphenylamine.

. The total reaction time was 11.5 hours.

6 Example 2 A mixture consisting of 155.6 parts (1.0 mol)mchloroformanilide, 157 parts (1.0 mol) bromobenzene, 172.6 parts (1.25mol) potassium carbonate, and 10 parts (0.081 mol) cupric carbonate washeated to reflux (166 C.) while being stirred. Any two-phase distillatethat appeared during this period was condensed and separated in anazeotropic distillation head, the water being discarded and thebromobenzene returned to the reaction vessel. As bromobenzene wasconsumed the temperature rose, in 55 minutes, to 207 C. The reactionmass was held at 205:5" C. for v10 hours, cooled, and extracted with 800parts carbontetrachloride. The extract after being filtered throughCelite (a filter aid) was concentrated in vacuo and then distilled togive:

Fraction Press. Wt., an

mm. Hg

IB.P.,

0. Parts Fractions A and B combined represent a yield of approximately74% of 3-chlorodiphenylamine containing roughly 10% of the N-formylderivative as determined by analysis of the infrared spectrum.

Fraction A was redistilled to yield as a main cut, 95.0 parts (46.6%yield) of substantially pure m-chlorodiphenylamine, identical to anauthentic sample in boiling range (117-120 C. at 0.2 mm. Hg), refractiveindex (11 1.6503), quantitative elemental analysis (for C, H, N, Cl) andinfrared spectrum. This sample, now containing less than 5% of carbonylcompound, is suitable for conversion'into 2-chlorophenothiazine(approximately 60% yield, M.P. l98200 C.) by using with sulfur inpresence of iodine, following the method described in British Patent716,205.

In the above example simple distillation technics were employed inisolating the product. If pure 3-chlorodiphenylamine is required, i.e.,essentially free of carbonyl-containing impurity, the crude reactionproduct is fractionated through a packed multi-plate distillationcolumn, overall yields of at least 60% of rectified product beingobtained.

Example 3 The procedure of Example 2 was repeated using 311.2 partsm-chloroformanilide, 350 parts bromobenzene, 345 parts potassiumcarbonate and 25 parts copper carbonate. The reaction mass was cooled toabout 100110 C. and filtered. The inorganic filter cake was thoroughlywashed with approximately 600 parts chlorobenzene, and the combinedfiltrate and washings were stripped in vacuo of the solvent. The residue'was distilled at 0.2 to 0.5mm. of Hg to give 1.2 parts boiling at30-105 C. and 316.8 parts of crude 3-chlorodiphenylamine, B.P. 117-160C., 11 1.6458.

291.2 parts of the crude 3-chlorodiphenylamine wa rectified at 10 mm. Hgpressure through a 24-inch column (rated at about 20 theoretical plates)and at a reflux ratio of 10/ 1.

Percent Carbonyl 1 OrPlOOD' 99999 39 5 osbsoooworrow lntrared analysis:The impurity in fraction 1 is m-chloroformanilide; fractions 6 and 7show high content of N -formyl 3-chlorodiphenylamine. Fractions 2, 3, 4and 5 represent a 67.9% yield of 3-chlorodiphenylamine.

Example 4 A mixture consisting of 155.6 parts (1 mol)rn-chloroformanilide, 157 parts (1 mol) bromobenzene, 207 parts (1.5mols) potassium carbonate, and 10 parts (0.081 mol) cupric carbonatewastreated as described in Example 2. The temperature rose from the initialreflux temperature of 167 C. to 208 C. in 1.5 hours. After being held atabout 210 C. for 10 hours, the reaction mass was cooled to 100 C. andstirred into 1000. parts water. The water-immiscible organic layer wasremoved and distilled:

Fraction B.P., Press, Wt., m.

C. mm. Hg Parts Fraction A corresponds to a 70% yield ofm-chlorodiphenylarnine containing less than of carbonyl compound. B andC arelesspure in that they contain larger quantities of carbonylcompound as shown by their infrared absorption spectra. Pure3-chlorodiphenylamine (13.1. 120:5 C. at 0.1 to 0.3 mm. Hg, 11;?"1.6503) may be obtained free of carbonyl impurity by rectificationthrough a multi-plate distillation column.

Example 5 The oily crystalline residue was recrystallized from 220 partsof methanol to yield 119.3 parts of 4-methoxydiphenylamine, M.P. 101103C. in 59.9% yield. Further recrystallization from methanol or benzeneraises the melting point to a maximum of 105106 C. 4-methoxydiphenylami-ne, prepared from p-acetoanisidine and bromobenzene,is reported to melt at 105 C. land and Wecker, Ber. 43, 708).

Example 6 A mixture consisting of m-chloroformanilide, 155.6

parts; bromobenzene, 157 parts; sodium carbonate, 159 parts; coppercarbonate, 3.5 parts was heated to reflux while being stirred; thetemperature of the stirred reaction mass rose to 208 C. in 2 hours. Thereaction mass was then held at 200210 C. for hours. During this time,any two-phase condensate which appeared was separated in an azeotropicdistillation head, the water being discarded and the bromobenzenereturned to the reaction vessel. The mixture was cooled somewhat and 165parts methanol was added slowly (any methanol vaporized by the'hotmixture was condensed and returned to the reactionvessel), followed by118 parts concentrated (36% by wt.) hydrochloric acid. The mixture washeated under reflux for 4 hours and then drowned in 850 parts water. Theoil layer was separated and distilled at reduced pressure to give 149parts (73% yield) of pure 3-chlorodiphenylamine.

In general when this experiment is repeated using sodium carbonate andthe crude N-fonnyl-3-chlorodiphenylamine is hydrolyzed in hot alcoholicmineral acid or in hot alcoholic alkali, the yields of pure3'-chlorodiphenylamine range from 70 to 80%.

If m-chloroacetanilide (169.7 parts) is employed instead ofm-chloroformanilide (155.6 parts) in the above example, the timerequired for the temperature of the The reaction mass was cooled,extracted reaction mass to reach 208 C. is 8 hours. Holding the reactionmass at ZOO-210 C. for 16 hours more and then hydrolyzing and working upas described above gives pure 3-chlorodiphenylamine in yields of toSince in general it is found that increasing the reaction time-at 210 C.results insomewhat better yields, the above example shows thatrn-cbloroformanilide is much more reactive than m-chloroacetanilideunder comparable conditions and alfords higher yields of3-chlorodiphenylamine.

In the above examples powdered metallic copper or copper bronze orcopper salts, e.g., cuprous iodide or chloride, may replace cupriccarbonate with similar results being obtained.

In the examples given, the reactors were heated by electrical means;however, for commercial use, especially on a large scale, it ispreferred to circulatehot vapor, such as superheated steam or a hotliquid, such as Dowtherm through a jacketed vessel to maintain thereaction mass at the desired temperature within the range of -240 C.This latter method of heating avoids local overheating and charring ofthe charge resulting in improved overall yields of the desired endproduct.

Substantially identical results are achieved in Examples 1 to 5 byreplacing formanilide and m-chloroformanilide by other substitutedformanilides such as Z-methylforrnanilide, 4-methylformanilide,3-ethylformanilide, 3,4- dimethylformanilide, and 3-methoxyformanilideto yield directly the corresponding unsymmetrical diphenyl- Likewise,instead of bromobenzene and 4- methoxybromobenzene in the aboveexamples, analogs and homologs such as 3-bromoethylbenzene,4-iodotoluene, S-methoxybromobenzene, 4-ethoxyiodobenzene and3-chloroiodobenzene may be employed with any of the formanilides listedabove to produce directly the symmetricallyandunsymmetrically-substituted diphenylamines described earlier in thespecification. Thus, condensation of m-chloroformanilide with3-chloroiodobenzene yields 3,3-dichlorodiphenylamine; condensation of3-methoxyformanilide with 3-methoxyiodobenzene yields3,3'-dimethoxydiphenylamine; condensation of N-formylp-toluidine with4-ethoxyiodobenzene yields 4-methyl-4- ethoxydiphenylamine.

If the corresponding N-acetylanilines are employed in the above Examples1 to 5 the products are the N-acetyldiphenylamines. In a controlexperiment using m-chloroacetanilide it is found that the time requiredfor the temperature of the reaction mass to rise to the preferredmaximum temperature of about 210 C. is about 4 times and the overallreaction time about 2 times that for the m-chloroformanilide. To convertthe resulting reaction mass to 3-chlorodiphenylamine it has to be heatedfor 3 to 4 hours in alcoholic hydrochloric acid or in alcoholic causticto split 01f the acetyl group. Best yields obtainable under theseconditions are 60-65%. On the other hand, if the reaction mass obtainedin controlled experiments using m-chloroformanilide is also subjected tothe same hydrolytic conditions the yield of 3-chlorodiphenylamine bythis longer process is of the order of 7079%.

The process of the present invention offers unexpected and beneficialresults. The formanilides are more easily and more economicallyprepared, requiring only' aqueous formic acid for formylation whereasacetylation is best accomplished by means of the anhydride. Furthermore,the formanilides are much faster reacting in the Ullmann condensation,in general about half the time being required to obtain yields ofdiphenylamine which are on this: average higher than those obtainablewith the acetani- As many apparently widely different embodimentsof thisinvention may be made without departing from the spirit and scopethereof, it is to be understood that the invention is not limited to thespecific embodiments thereof except as defined inthe appended claims.

The embodiments of the invention in which. an exclusive property orprivilege is claimed are defined as follows:

1. The process of preparing symmetrical and unsymmetrical diphenylamineswhich process comprises reacting (A) a compound taken from the groupconsisting of formanilide, alkyl-substituted formanilides,alkoxylsubstituted formanilides, fiuoro-substituted formanilides, andchloro-substituted formanilides with (B) a compound taken from the groupconsisting of bromobenzene, iodobenzene, alkyl-substituted bromobenzene,alkoxylsubstituted bromobenzene, fiuoro-substituted bromobenzene,chloro-substituted 'bromobenzene, alkyl-substituted iodobenzene,alkoxyl-substituted iodobenzene, fluorosubstituted iodobenzene, andchloro-substituted iodobenzene in the presence of a copper Ullmanncondensation catalyst and potassium carbonate at a temperature withinthe range of 170 to 240 C. and recovering the corresponding diarylaminedirectly from the reaction mass.

2. The process of claim 1 wherein the Ullmann condensation catalyst istaken from the group consisting of copper, copper bronze, cuprouschloride, cuprous bromide, cuprous iodide and cupric carbonate.

3. A process for the preparation of 3-chlorodiphenylamine whichcomprises reacting m-chloroformanilide with bromobenzene in the presenceof cupric carbonate as catalyst and potassium carbonate as acid-acceptorat a temperature within the range of 170 to 220 C. and recovering the3-ch1orodiphenylamine from the reaction mass.

4. The process for the preparation of 3-chlorodiphenylamine whichcomprises reacting m-chloroformanilide with bromobenzene in the presenceof a copper Ullmann condensation catalyst and sodium carbonate asacidacceptor at a temperature within the range of 170-220 (3., followedby hydrolysis of the resulting N-formyldiphenylamine and recovering3-chlorodiphenylamine from the reaction mass.

5. The process of claim 4 wherein the copper Ullmann condensationcatalyst is taken from the group consisting of copper powder, copperbronze, cuprous bromide,

cupric carbonate, cuprous iodide and cuprous chloride.

References Cited in the file of this patent UNITED STATES PATENTS SmithOct. 23, 1951 OTHER REFERENCES

